In a small corner plot in Esher, Surrey, Oliver Leech Architects has designed a multifaceted, charred-timber home for the mother of its client. You’d be forgiven for thinking that this was a stand-alone house, rather than a compact one-storey garden suite. “They came to us to create a granny flat, but the resulting house doesn’t feel or look like that at all,” says Oliver Leech, the London studio’s director. “Other than sharing a garden, it could be its own house, which I think is part of the success of the design.”

With its blackened envelope, origami-style green roof (expressed visually as a butterfly configuration, hence the project’s name) and four pitched volumes angled to create a fan-like shape, the 94-square-metre home was designed to fit as discreetly as possible into the triangular site at the bottom of the garden and prevent overlooking or direct views into or out of it. “We didn’t want a big window that would face straight back into the main family home and that you could see into,” explains Leech. “You can catch some glimpses into the corners of the living space, but that’s all. And you don’t see into the bedrooms at all, because they are set back.”

The butterfly roof floats above the kitchen, creating a stepped clerestory. The kitchen, including its island on casters, is by Weymont & Wylie.

Despite being tucked away and surrounded by trees, the annex achieves a sense of airiness and spaciousness through a variety of architectural moves. The roof, which is lowest by the  boundaries of the property, reaches its tallest point in the middle, where a central spine allows for a row of clerestory windows along the main, west-facing hallway, which bathes the open-plan living space in natural illumination and offers alluring views to the treetops blowing in the breeze. In the bedrooms, the architects decided to double-space the rafters to increase the feeling of light and height. In the bathrooms, Velux skylights were used to similar effect; the one in the primary bathroom has a mirror below it that visually doubles the size of the glazing and reflects a tree behind the house.

The single-storey plan puts the kitchen and living area front and centre. A warm palette and polished concrete floors provide a sense of expansiveness.

The house has been designed to accommodate elderly living, but it’s very much a case of futureproofing rather than responding to existing needs, explains Leech. The mother of the client, like her daughter, has enjoyed a career as a geologist. “The first time we met her, she came bounding up to us after driving back from Switzerland, where she had been skiing,” recalls Leech. “The design will allow for her to grow old here but also for the spaces to be used for other purposes if necessary.”

A view into the living area, where the roof’s flitched central ridge beam dips down to evoke a sense of depth.

Among the accessibility features are level thresholds between the doors and windows and the patio outside, a ramp into the kitchen and living spaces, low drawers in the kitchen, and open-plan showers (without trays) in the two bathrooms. The skylights in the latter spaces are also remotely operated, lest opening the windows manually becomes more difficult, and the second bedroom and bathroom could be used by a future live-in caregiver.

The material palette is purposely natural and soft. Windows, doors and ceiling joists made of larch imbue warmth, calmness and texture, as do oak floors in the bedrooms and polished concrete in the rest of the house. “The clay plaster walls bounce light around and have a lovely mottled, imperfect look,” says Leech. The architects made a conscious decision to expose the building’s timber frame and structure. “It was quite a complex structural solution, and such an interesting roof shape, that we thought it would be a shame to cover it. This way, you can really appreciate the geometries and the structure that has gone into building the house.”

A compressed, curved entrance opens onto a lofty living area. The natural clay plaster walls are by Clayworks.

Leech’s favourite space is the entrance lobby, where the four volumes and roof geometries converge. It doesn’t have any windows of its own but borrows light from other rooms, resulting in a slightly more subdued and reflective ambience; its curved walls enclose you in a compressed space before you enter the living areas proper. Like everything in this house, it is well-crafted, considered and uplifting, countering any elderly-living or accessible-design tropes with a deftness of touch.